entropy

The coefficients have to come from somewhere. This is the somewhere, and it is running while you read.

counts

where it comes from

Every byte drawn on this page comes from the operating system, through the browser, by way of crypto.getRandomValues. It is the same source your session keys are drawn from, and it is not a function of the time, the page, or anything you did.

This matters more than it looks. A shard reveals nothing only if the coefficients hiding it were unguessable. Predictable coefficients turn the whole scheme into a formality: the shards still look like shards, they still reconstruct correctly, and they protect nothing whatsoever.

The plot is a bit field: one column per byte drawn, one row per bit position, lit where the bit is set. There is nothing to see in it, and that is the point. Any pattern that ever appeared here would mean something had gone badly wrong upstream.